U.S. patent number 6,477,595 [Application Number 09/547,921] was granted by the patent office on 2002-11-05 for scalable dsl access multiplexer with high reliability.
This patent grant is currently assigned to E-Cell Technologies. Invention is credited to K. C. Babu, R. Balasubramanyam, Michael S. Cohen, P. K. Nanda Kumar, Murali Ramanathan.
United States Patent |
6,477,595 |
Cohen , et al. |
November 5, 2002 |
Scalable DSL access multiplexer with high reliability
Abstract
A digital subscriber line (DSL) multiplexer is used in
conjunction with a DSL modem to provide a reliable high speed
connection for an end-user. The scaleable DSL multiplexer supports
multiple DSL modems to a number of subscriber desiring increased
bandwidth. The connection is reliably maintained by the multiplexer
which utilizes a proprietary protocol to exchange management
information to monitor the connection.
Inventors: |
Cohen; Michael S. (Enola,
PA), Babu; K. C. (Bangalore, IN), Balasubramanyam;
R. (Bangalore, IN), Ramanathan; Murali
(Bangalore, IN), Kumar; P. K. Nanda (Bangalore,
IN) |
Assignee: |
E-Cell Technologies (Austin,
TX)
|
Family
ID: |
26857817 |
Appl.
No.: |
09/547,921 |
Filed: |
April 11, 2000 |
Current U.S.
Class: |
710/105;
379/93.14; 379/93.28; 710/104 |
Current CPC
Class: |
H04L
12/5601 (20130101); H04L 12/5692 (20130101); H04L
41/00 (20130101); H04L 49/351 (20130101); H04M
11/062 (20130101); H04Q 11/04 (20130101); H04Q
11/0478 (20130101); H04L 49/3009 (20130101); H04L
2012/561 (20130101); H04L 2012/5618 (20130101); H04L
2012/5635 (20130101); H04L 2012/5651 (20130101); H04L
2012/5665 (20130101); H04Q 2213/13039 (20130101); H04Q
2213/1305 (20130101); H04Q 2213/13097 (20130101); H04Q
2213/13103 (20130101); H04Q 2213/13106 (20130101); H04Q
2213/13109 (20130101); H04Q 2213/13162 (20130101); H04Q
2213/13164 (20130101); H04Q 2213/13166 (20130101); H04Q
2213/1319 (20130101); H04Q 2213/13199 (20130101); H04Q
2213/13204 (20130101); H04Q 2213/13216 (20130101); H04Q
2213/13248 (20130101); H04Q 2213/1329 (20130101); H04Q
2213/13292 (20130101); H04Q 2213/13299 (20130101); H04Q
2213/1332 (20130101); H04Q 2213/13322 (20130101); H04Q
2213/1334 (20130101); H04Q 2213/13389 (20130101) |
Current International
Class: |
H04M
11/06 (20060101); H04L 12/56 (20060101); H04L
12/24 (20060101); H04Q 11/04 (20060101); H04L
12/28 (20060101); H04L 12/413 (20060101); H04L
12/407 (20060101); G06F 013/42 () |
Field of
Search: |
;379/93.14,93.28
;710/104,105 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
T Jessup, "DSL: The Corporate Connection ", Feb. 1, 1998, pp.
103-110. .
PCT Int'l Search Report (7 pp)..
|
Primary Examiner: Dharia; Rupal
Attorney, Agent or Firm: McDermott, Will & Emery
Parent Case Text
This application claims the benefit of U.S. Provisional Application
No. 60/161,420, filed Oct. 25, 1999, which is fully incorporated
herein by reference.
Claims
What is claimed is:
1. A multiplexing device for providing high speed network
connectivity for the transport of data frames to at least one
subscriber, comprising: a digital subscriber line (DSL) transceiver
interface coupled to a plurality of subscriber DSL modems; a packet
buffer coupled to the DSL transceiver interface for storing the
data frames, the packet buffer transferring the data frames over a
packet buffer bus; an Ethernet-type port coupled to the packet
buffer for uplinking to an external switch; and a central
processing unit (CPU) coupled to the packet buffer for executing
code to send and receive proprietary protocol packets for
communicating management information associated with the plurality
of subscriber DSL modems, the management information indicating
presence of an Ethernet-type port, current line speed, and media
access control (MAC) address; wherein the proprietary protocol
packets comprise: a line identification field that identifies a
subscriber line associated with one of the subscriber DSL modems; a
sequence identification field that is used for synchronization
between the data frames; a data length field that specifies the
length of a data payload within the data frames; and a checksum
field for error detection.
2. The multiplexing device as in claim 1, further wherein an
external POTS splitter supplies DSL signals to the DSL transceiver
interface.
3. The multiplexing device as in claim 1, further wherein the
subscriber DSL modem and the DSL transceiver interface utilize a
rate adaptive DSL scheme.
4. The multiplexing device as in claim 1, wherein the Ethernet-type
port is a 100Baset-T port, wherein the Ethernet-type port supports
full duplex operation.
5. The multiplexing device as in claim 1, further comprising a
cross-point switch coupled to the DSL transceiver interface for
modem pooling, wherein the DSL transceiver interface comprises six
DSL modems to support at least twenty-four subscribers.
6. The multiplexing device as in claim 1, wherein the management
information comprises lower and upper Service Access Point (SAP)
information.
7. The multiplexing device as in claim 1, wherein the management
information comprises a file download module for retrieving a
runtime file from the multiplexer, wherein the runtime file, when
executing, is configured to forward data from the DSL transceiver
interface to the Ethernet-type port, forward data from the
Ethernet-type port to the DSL transceiver interface, control
operation of the DSL transceiver interface, and share the DSL
transceiver interface among the plurality of subscriber DSL
modems.
8. The multiplexing device as in claim 1, wherein the DSL
transceiver, the packet buffer, the Ethernet-type port, and the CPU
are housed in a stackable chassis.
9. A multiplexing device for providing high speed network
connectivity for the transport of data frames to at least one
subscriber, comprising: a digital subscriber line (DSL) transceiver
interface coupled to a plurality of subscriber DSL modems; a packet
buffer coupled to the DSL transceiver interface for storing the
data frames, the packet buffer transferring the data frames over a
packet buffer bus; an Ethernet-type port coupled to the packet
buffer for uplinking to an external switch; and a central
processing unit (CPU) coupled to the packet buffer for executing
code to send and receive proprietary protocol packets for
communicating management information associated with the plurality
of subscriber DSL modems, the management information indicating
presence of an Ethernet-type port, current line speed, and media
access control (MAC) address; wherein the management information
comprises a file download module for retrieving a runtime file from
the multiplexer, wherein the runtime file, when executing, is
configured to forward data from the DSL transceiver interface to
the Ethernet-type port, forward data from the Ethernet-type port to
the DSL transceiver interface, control operation of the DSL
transceiver interface, and share the DSL transceiver interface
among the plurality of subscriber DSL modems.
Description
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a digital subscriber line (DSL)
multiplexer for providing connectivity to a data network. In
particular, the present invention involves the exchange of
management information from the DSL multiplexer to an end-user DSL
modem.
2. Background Art
As the information age matures, it is enabled by a number of
technological advances, such as the geometric growth of networked
computing power and the prevalence of reliable and ubiquitous
transmission media. Today's consumers in both the residential and
business arena have been acclimated to a more graphical approach to
communication. In particular, multimedia applications (which
include textual, graphical, image, video, voice and audio
information) have become increasingly popular and find usage in
science, business, and entertainment. Local area networks (LANs)
are essential to the productivity of the modem workplace;
Ethernet-type networks have dominated the LAN market and have been
continually enhanced (e.g., switched Ethernet, Fast Ethernet,
and/or Gigabit Ethernet) to keep pace with the bandwidth intensive
multimedia applications.
A compelling example of the growth of information consumption is
the dramatic increase in users of the World Wide Web, a
multimedia-based information service provided via the Internet.
Although initially a forum for academia to exchange ideas captured
in ASCII text, the Internet has developed to become a global media
for users from all walks of life. These Internet users regularly
exchange multimedia graphical, image, video, voice and audio
information as well as text.
Furthermore, the business world has come to realize tremendous
value in encouraging workers to telecommute. To avoid the idle
commuting time, today's workers enjoy the convenience of working
from home via their personal computers. As illustrated in FIG. 1A,
a user at a remote site 101 (e.g., home) has traditionally been
able to access her/his office 119, which includes accessing an
office local area network 119b (LAN), through a dial-up connection
over a 33 Kbps or 56 Kbps modem 101b. The dial-up connection is
handled by a telephone communication facility 240 (CO) 105 through
a voice switch 107, which switches the "data" call through a public
switched telephone network (PSTN) 111. The data call terminates in
a remote CO 121 at a voice switch 123. The voice switch 123
switches the call to the subscriber; in this case, the called line
is associated with a modem in a modem pool 119a. Once connected to
the modem pool 119a, the end user at her/his remote site 101 can
access the computing resources in his office 119. These sources
include a multimedia server 119c and a PC 119d of the remote user.
A similar connection to Internet 115 by a user at a remote site 101
can be accomplished by connecting to an Internet Service Provider
(ISP) 117 instead of modem pool 119c.
Unfortunately, telecommuting from a remote office or accessing
multimedia information from home over the Internet imposes an
enormous strain on networking resources. It is common knowledge
that the networking infrastructure is the bottleneck to the
expedient transfer of information, especially bandwidth intensive
multimedia data. As alluded to before, today's access methods are
limited to standard analog modems, such as 101b, which have a
maximum throughput of 56 Kbps on a clean line (i.e., a line not
having any appreciable noise causing errors in bit rate transfer).
Remote users may alternatively acquire basic rate (2B+D) Integrated
Services Digital Network (ISDN) services at 128 kbps. Even at this
speed, telecommuters may quickly grow impatient with slow response
times as compared to the throughput of their LANs to which they
have grown accustomed. On average, a typical Ethernet user can
expect to achieve approximately 1 Mbps on a shared 10Base-T
Ethernet LAN and up to 9+Mbps in a full duplex switched Ethernet
environment. In addition, Internet users are also demanding greater
access speeds to cope with the various multimedia applications that
are continually being developed. Fortunately, the communication
industry has recognized the escalating demand.
Cell switching technology, such as Asynchronous Transfer Mode
(ATM), was developed in part because of the need to provide a
high-speed backbone network for the transport of various types of
traffic, including voice, data, image, and video. An ATM network
113 is typically able to provide bandwidths to an ATM user at
approximately 1.5 Mbps on a T1 line, 44.7 Mbps on a T3 line, and
155 Mbps over a fiber optic OC-3c line. Consequently, ATM networks
are suitable to transport multimedia information.
ATM further provides a mechanism for establishing quality of
service (QoS) classes during the virtual channel setup, thereby
allotting a predetermined amount of bandwidth to the channel. QoS
classes define five broad categories that are outlined, for
example, by the ATM Forum's UNI 3.0/3.1 specification. Class 1
specifies performance requirements and indicates that ATM's quality
of service should be comparable with the service offered by
standard digital connections. Class 2 specifies necessary service
levels for packetized video and voice. Class 3 defines requirements
for interoperability with other connection-oriented protocols,
particularly frame relay. Class 4 specifies interoperability
requirements for connectionless protocols, including IP, IPX, and
SMDS. Class 5 is effectively a "best effort" attempt at delivery;
it is intended for applications that do not require guarantees of
service quality.
In conventional data networks, such as the typical Ethernet LAN or
X.25 WAN, there are no explicit negotiations between the network
and the user specifying the traffic profile and quality of service
expected. Rather, the network is expected to provide each user with
a "fair share" of the available bandwidth.
However, in an ATM network, fair allocation of bandwidth requires
users to adjust their transmission rates according to the feedback
from the network. ATM networks carry fixed bandwidth services
required for multimedia applications (constant bit rate (CBR)
traffic) and guaranteed bandwidth services for high-priority data
applications (variable bit rate (VBR) traffic). The remaining
bandwidth, not used by guaranteed bandwidth services, must be
shared fairly across all users. The ATM Forum refers to services
that make use of this otherwise idle bandwidth as available bit
rate (ABR) services.
Although these ABR applications must contend for remaining
available bandwidth and would not provide specific throughput
guarantees, ABR applications still would require fair access to the
available bandwidth with a minimum of cell loss. If ABR traffic had
no mechanism to determine if sufficient bandwidth were available to
handle the transmission on the network and traffic was simply fed
in, network congestion might result in dropped cells, and
application traffic might be lost. ABR flow control is an ATM layer
service category for which the limiting ATM layer transfer
characteristics provided by the network may change after
establishing the network connection. A flow control mechanism is
specified which supports several types of feedback to control the
source rate in response to changing ATM layer transfer
characteristics. When the network becomes congested, the
end-stations outputting ABR traffic are instructed to reduce their
output rate. It is expected that an end-system that adapts its
traffic in accordance with the feedback will experience a low cell
loss ratio and obtains a fair share of the available bandwidth
according to a network-specific allocation policy. Cell delay
variation is not controlled in this service, although admitted
cells are not delayed unnecessarily.
In this end-to-end rate-based scheme, the source (e.g., a user
remote site 103) of a virtual circuit (VC) indicates the desired
rate in a resource management cell (RM cell). An RM cell is a
standard 53-byte ATM cell used to transmit flow-control
information. The RM cell travels on the VC about which it carries
information, and is therefore allowed to flow all the way to the
destination end-station (e.g., PC 119d ). The destination reflects
the RM cell, with an indicator to show that the RM cell is now
making progress in the reverse direction. The intermediate switches
(e.g., switch 109) then identify within the reverse RM cell their
respective maximum rates (the explicit rate allocated to the VC).
After the source receives the reverse RM cell, the smallest rate
identified in the reverse RM cell is then used for subsequent
transmissions until a new reverse RM cell is received.
ATM has many recognized advantages and has dominated wide area
networks (WANS) as the preferred backbone transport technology.
Because of cost and performance factors, ATM faces stiff
competition from both switched and shared-media high-speed LAN
technologies, including Ethernet, Fast Ethernet, and Gigabit
Ethernet. And although ATM typically offers QoS guarantees superior
to the prioritization schemes of competing high-speed technologies,
many users remain unable to take advantage of these features. If a
remote user wishes to obtain the advantages of ATM, one solution
would be to acquire an ATM switch on the premises as shown in FIG.
1A. The remote site 103 would need to be equipped with an ATM
switch 103a, whereby a PC 103b interfaces the ATM switch 103a via
an ATM NIC 103c. In addition, the remote user would have to lease a
T1 line or an OC-3c pipe from the Telco. The leased line would
terminate in an ATM switch 109 in the CO 105. The CO ATM switch 109
is connected to the ATM network 113. With an ATM connection, the
remote user may quickly access multimedia information on the
Internet by establishing a virtual channel that would terminate at
ATM switch 125 in CO 121. The CO 121 would of course have some
means of communication with the ISP 117; typically routers (not
shown) are used.
Alternatively, FIG. 1B illustrates an ATM to the desktop solution
whereby the xDSL technology is utilized to extend ATM capability
remotely. At the customer premises 103, a PC 103b is equipped with
an ATM NIC 103c, which is attached to an xDSL modem 103d. In
addition, a telephone set 103e is linked to the xDSL modem 103d.
The xDSL modem is connected over twisted pair copper wire to the CO
105, terminating at the POTS splitter 117. The POTS splitter 117
separates the data signals originating from the PC 103b from the
voice signals. A xDSL multiplexer (mux) 115 receives the data
signals from the POTS splitter and uplinks these signals to the ATM
switch 105. Although the solution present above provides a way to
deliver ATM capabilities to the desktop, it disadvantageously
requires the acquisition of ATM NICs by the remote users, and the
xDSL modem has to have a costlier ATM interface.
Despite all the many inherent advantages with ATM, Ethernet-type
LANs constitute nearly all of the networking resources of business
and residential users. Moreover, these legacy systems are still
being enhanced and marketed, e.g., switched Ethernet, switched Fast
Ethernet, and switched Gigabit Ethernet are significantly lower
cost than their ATM counterparts. ATM technology requires a
substantial investment in infrastructure, from cable plant to
switches to network interface cards (NICs). This tremendous
investment cost can be sustained in the wide area network (WAN)
where costs can be spread out. However, in the LAN environment, the
investment in infrastructure is typically unsustainable which
translates into retention of "legacy" LANs such as Ethernet.
While a number of service providers (e.g., Telcos) employ ATM to
establish point-to-point circuits, little has been done to utilize
ATM for transporting multimedia information or services to the
desktop. This is simply not commercially practical. As previously
noted, commercial practicality prohibits such an endeavor. In
essence, millions of users would be required to purchase expensive
ATM network interface cards, and then possibly add very costly T1,
T3, or OC-3c lines. As a result, service providers have not
commercially implemented ATM in the delivery of multimedia
information to the desktop.
One apparent disadvantage is the inability of current access
techniques to adequately provide bandwidth to the end user for
access to networking resources.
Another disadvantage is the high cost related to procuring
sufficient bandwidth to alleviate long delays caused by low speed
connection.
DISCLOSURE OF THE INVENTION
There is a need for an arrangement that enables the high-speed
transmission of multimedia information to the desktop.
There is also a need for an arrangement that enables use of an
Ethernet-type network interface device to access a high speed cell
switching network.
There is also a need for an arrangement that ensures reliable
connectivity to networking resources.
These and other needs are attained by the present invention, where
a digital subscriber line (DSL) multiplexer employs a proprietary
protocol to communicate with an end user DSL modem to monitor the
connection.
According to one aspect of the present invention, a multiplexing
device for providing high speed network connectivity for the
transport of data frames to at least one subscriber, comprises a
digital subscriber line (DSL) transceiver interface coupled to
plurality of subscriber DSL modems. A packet buffer is coupled to
the DSL transceiver interface for storing the data frames. The
packet buffer transfers the data frames over a packet buffer bus.
An Ethernet-type port is coupled to the packet buffer for uplinking
to an external switch. A central processing unit (CPU) is coupled
to the packet buffer for executing code to send and receive
proprietary protocol packets for communicating management
information associated with the plurality of subscriber DSL modems.
The management information indicates presence of an Ethernet-type
port, current line speed, and media access control (MAC)
address.
Additional advantages and novel features of the invention will be
set forth in the description which follows, and in part will become
apparent to those skilled in the art upon examination of the
following or may be learned by practice of the invention. The
advantages of the invention may be realized and attained by means
of the instrumentalities and combinations particularly pointed out
in the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Reference is made to the attached drawings, wherein elements having
the same reference numeral designations represent like elements
throughout and wherein:
FIGS. 1A and 1B are graphic representations of a prior art networks
and the access methods;
FIGS. 2A and 2B are block diagrams depicting detailed aspects of
systems incorporating a multiplexer configured in accordance with
the present invention;
FIG. 3 is a block diagram of the hardware architecture of a DSL
multiplexer in accord with one embodiment of the present
invention;
FIG. 4 is a block diagram illustrating a boot code
architecture;
FIG. 5 is a block diagram illustrating a runtime code
architecture;
FIG. 6 is a block diagram of a standard Ethernet type 2 packet
format;
FIG. 7 is a block diagram of a data field of a proprietary protocol
PDU; and
FIG. 8 is a block diagram of a generic PDU format for exchanging
information in accordance with the present invention.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention provides a high speed connection to the end
user through a digital subscriber line multiplexer. This retains
the traditional low cost and low complexity associated with
Ethernet technology while achieving QoS. NIC but achieves ATM
capability over Ethernet through use of an Ethernet edge switch
which employs a multi-processor architecture to interface an
Ethernet environment with an ATM infrastructure.
FIG. 2A illustrates an embodiment of the present invention taking
advantage of the existing network media created by the telephone
industry which implemented a vast network of copper twisted pair
wiring to interconnect homes and businesses domestically and
abroad. In FIG. 2A, a customer premises 200 is shown as comprising
an end-station 210, such as a desktop computer residing in a home
or business. Typically, such end-stations are either stand-alone
desktop stations, or are already connected to a collocated local
area network (LAN).
A variety of LAN technologies exist, but the large majority of LANs
conform to the IEEE standard 802.3, which defines Ethernet
standards. Various types of Ethernet systems exist such as switched
Ethernet, Fast Ethernet, and Gigabit Ethernet. The end-station 210
is equipped with an Ethernet NIC 212 residing in a personal
computer with a host processor 214. Ethernet NIC 214 is connected
to a high-speed digital subscriber line (DSL) modem 220, which
interfaces with a telephone line 222 via a CP (customer premise)
POTS (plain old telephone service) splitter 221. The telephone line
is a twisted pair copper wire, which the conventional customer
premises telephone 224 uses to connect with a telephone
communication facility 240. A telephone communication facility 240
or end office is shown in FIG. 2A as a communications facility 240;
however, any communication facility can be used (e.g., a wire
closet in a separate building).
High-speed communication to remote users depends largely on the
method of access to the networking infrastructure. Most users
cannot bear the cost of leasing expensive outside lines that are
needed to provide high speed communication to the Internet or to
their offices. The disclosed embodiment overcomes this dilemma by
employing a high-speed, low cost subscriber interface that takes
advantage of the legacy outside cable plant, such as standard
twisted copper pair wiring and coaxial cables.
One embodiment, shown in FIG. 2A, utilizes digital subscriber line
(DSL) technology to delivery the high bandwidth that the remote
users demand. Because traditional copper cabling is used, the
remote users do not have to upgrade their current physical
connection--their POTS line is sufficient. Because the outside
plant need not be revamped, telephone companies (Telcos) can
readily implement DSL services. The DSL modem 220 acts as the
network access device to the communication facility 240. A DSL
multiplexer 252 provides termination of the DSL modem connection
within communications facility 240. DSL technology is categorized
by the downstream and upstream bandwidths. The present invention
could be applied to any of the various forms of DSL technology. One
variety, commonly employed, Rate Adaptive DSL or RADSL, involves a
rate negotiation between the customer premise DSL modem 220 and the
Telco CO modem located within DSL MUX 252 which takes into account
distance and line quality issues yielding the maximum available
rate for the line conditions encountered. RADSL supports both
Asymmetric DSL or ADSL, with a maximum downstream rate of 7.62 Mbps
and a maximum upstream rate of 1.1 Mbps, which is ideal for very
high speed Internet access and video-on-demand applications. ADSL
services can be delivered up to 18,000 feet from the communication
facility 240 over a single copper twisted pair. RADSL also supports
Symmetric DSL or SDSL, with a maximum bi-directional rate of about
1.1 Mbps, which is ideal for very high quality video-conferencing
and remote LAN access. Another type of DSL technology is known as
high-bit-rate digital subscriber line (HDSL), which provides a
symmetric channel, delivering T1 rates (1.544 Mbps) in both
directions. HDSL has a distance limitation of about 12,000 feet
without repeaters. Telcos have traditionally used HDSL to provide
local access to T1 services. HDSL is already widely deployed within
the Telco market as a low cost T-1 replacement. VDSL or Very high
bit-rate DSL requires a fiber-to-the curb local loop
infrastructure, with asymmetric speeds up to 52 Mbps. Other flavors
of DSL (i.e., sometimes generically denoted xDSL) are characterized
by whether the service is asymmetric or symmetric and the bandwidth
allocations for the upstream and downstream transmissions.
The communication facility 240 comprises a plain old telephone
service (POTS) splitter 242 which receives the information
transmitted across the twisted pair line 222 and "splits" the low
frequencies, which carry voice signals, from the high frequencies,
which carry data signals. Essentially, the POTS splitter is a
passband filter, whereby the low frequency information is carried
by a voice line 224 to a voice switch 246 and ultimately to a
public switched telephone network (PSTN) 248. The voice line 224,
voice switch 246 and PSTN 248 are each conventional, and are
therefore not explained further so as not to detract from the focus
of the disclosure of the present invention.
The data information, which is modulated using high frequency
signals, is transmitted over a twisted pair cable 250 to a POTS
splitter 242. The POTS splitter 242 then passes the high frequency
signals to a DSL multiplexer (DSL MUX) 252. The DSL MUX serves as
the DSL modem termination point for numerous end users with DSL
modems. The DSL MUX 252 aggregates all the DSL traffic and passes
the multimedia information to the multimedia switch 260. The
traffic can be of any data type including multimedia graphics,
video, image, audio, and text. Various embodiments of the DSL MUX
252 can be employed, ranging from 24 line stackable modules through
the traditional high density chassis based approach. Various line
codes can be supported within the DSL modems, including Carrierless
Amplitude Phase (CAP) modulation, Discrete Multi-Tone (DMT)
modulation, Quadrature Amplitude Modulation (QAM), as well as
others. Multimedia switch 260 is primarily an edge device that is
connected to an ATM network 270 on which a conventional multimedia
server (not shown) may be linked. The ATM network 270 thus
represents a fast and efficient delivery system for multimedia
applications to which the end user desires access. The multimedia
switch 260 communicates with the CO DSL MUX 252 relative to traffic
information, in order to minimize congestion. Traditionally, end
user access to an ATM network has been through a router. Since the
end-station 210 houses an Ethernet NIC 214, connection to ATM
network 270 proves difficult without the system of the present
invention, which allows information residing on an ATM network to
be transferred to an Ethernet end-station while still retaining all
the multimedia benefits of ATM, including QOS and ABR/ER flow
control. An advantage associated with a DSL implementation is that
the personal computer is constantly connected, much like a typical
Ethernet LAN connection. That is, communication sessions are not
initiated through a dial-up procedure.
FIG. 2B is illustrates an other embodiment of the present invention
where DSL Mux 252 is able to connect to a plurality of DSL modems
220. This configuration enables many customer premise modems 220,
for example twenty four, to be pooled together. Further, the
multimedia switch 260 can accommodate multiple DSL multiplexers
252, thereby achieving a higher density of subscribers. The uplink
from the DSL multiplexer 252 to the multimedia switch 260 is
typically a fast Ethernet connection.
Turning now to FIG. 3, DSL multiplexer 252 comprises a number of an
ADSL modem devices based on CAP (Carrier-less Amplitude/Phase)
modulation technology, and is located within communication facility
240. The device will be used for Internet access and corporate
private network use. DSL multiplexer 252 has station 6 modems 300,
which can be connected to 24 subscriber lines (SL) (e.g., 222)
having customer premise modems, for example, DSL modem 220. DSL
multiplexer 252 also has two 100Base-T ports 302 to communicate
with multimedia switch 260. In such a configuration, multimedia
switch 260 will have up to 24 end stations, such as end station
210, connected to one 100Base-T port. One or more of these
end-stations can be CIF end stations. In order to deliver QoS to
these end stations, some information has to be passed between DSL
multiplexer 252 and multimedia switch 260. A specific protocol is
defined for this purpose. DSL multiplexer 252 can implement, for
example, the Intel 80960HD (i960HD) 32 bit RISC processor running
at 33 MHz.
Two 100BaseT ports 302 operate as one primary port and one standby
port. The standby port takes over the functions of the primary port
when the primary port fails and vice versa. At any time, only one
port will be active. 100BaseT port 302 is implemented in one
embodiment using Intel's 82557 MAC and external transceivers.
100baseT port 302 supports full duplex operation. Logic is provided
to drive the "link/activity" and "port disabled" LEDS. The physical
connector is a standard RJ45 jack.
Two DRAM based memory banks, i.e. a packet buffer 304 and a local
buffer 306, are implemented in one embodiment. Packet buffer 304 is
used for the DSL data and local buffer 306 is used as code memory
and workspace. Fast page EDO (Extended Data Out) DRAMs are used in
an embodiment for both memory banks, since they can work with zero
wait states in a 33 Mhz system without having to introduce memory
interleaving.
Remote access controller(RAC) 308 provides the MAC functions for
the 10BaseT port used for SNMP traffic. This port can also be used
as a high-speed debug port during software testing. External
10Base-T transceiver is provided. Logic is provided to drive the
"link/activity" and "port disabled" LEDs. The physical connector is
a standard 8 pin RJ45 jack. The RAC chip 308, for example the
Galileo Technology (GT96010), is used to interface the ADSL serial
data (to/from the GTI modem devices) to packet buffer 304. This
chip has six multi-protocol serial channels and an Ethernet port.
It has a DMA engine which is compatible with, for example, i960JX
processor. Some glue logic is required to interface this chip to
i960HD. Each GT96010 can currently support three ADSL channels at
maximum downstream data rate of 8 Mbps and an upstream rate of 1
Mbps. The two 100baseT uplink ports 302 can be implemented using
the Intel 82557 MAC chip. The 100baseT ports 302 support full
duplex operation.
A local bus 310 will support a CPU 312, local DRAM 306, a flash
memory 314, an EPROM 316, a NVSRAM (non-volatile static random
access memory) 318, control ports and status ports 320, a DUART 322
and a set of buffers 324 which connects to the other buses. Flash
memory 314 (512Kx8) is used for the storage of firmware. On
power-up, the filmware will be downloaded from Flash 314 into local
DRAM 306 (4MB) for execution. The boot code resides in EPROM 316.
DUART 322 provides (a) the PPP SNMP link (also used by a local
diagnostic and configuration utility) and (b) a debug port which is
used during the development cycle for testing and debugging the
board. All modem transceivers 300 sit on an 8 bit wide modem bus
325. Crosspoint switches 326 sit on an 8 bit wide switch bus
327.
Packet buffer 304 (4 MB) is used to store the frames from the DSL
multiplexer 252 interfaces (100BaseT and 10BaseT). The 100BaseT MAC
chips can be a PCI device and can connect to packet buffer 304
through a PCI bridge 330. CPU 312 accesses the packet memory
through buffer 304. Remote access controller (RAC) chip 308 is used
to provide the 10BaseT interface for SNMP traffic. The six modem
transceivers 300 are interfaced to the packet buffer 304 using two
remote access controllers 309. All the above masters on a packet
bus 332 operate with multiplexed address and data. A common address
latch 334 is used to route the addresses to packet buffer 304.
Arbitration among the contenders for packet buffer 304 is done in
round robin fashion.
Two serial ports 323, operating at a maximum speed of 38.4 Kbps
will be provided by using DUART chip 322. One serial port will be
used for SNMP traffic over a PPP (point-to-point protocol) link.
The same serial port can also be used for running the local DSL
multiplexer 252 diagnostics utility. This port will also support a
null modem connection (auto-answer only). The second serial port
will be used only during development for debugging the card. The
physical connector for each port is a 9 pin D-Sub receptacle.
The transceiver interface will be based on a RADSL chipset
implemented as DSL modem 220. Six modem chipsets will be used to
connect to 24 subscriber lines through a cross point switch. The
GT96010 multi-channel serial controllers will be used to interface
the transceivers to packet buffer 304. Each controller provides
three ADSL interfaces and a DMA engine supporting data bursts to
the memory. DSL multiplexer 252 will use an external POTS splitter
242. One 50 pin champ connector will be used for the incoming DSL
lines from POTS splitter 242.
The two control ports 320 use 32 bits, of which some bits are used
as individual resets to the various controllers. 48 bits drive DSL
status LEDs, 2 bits drive health/diagnostics LEDs, and 2 bits drive
power-supply status LEDs. Three 8-bit ports control the power to
line-drivers (SLIDES) 336. A fourth 8-bit port provides individual
resets to modem transceivers 300. One 32-bit status port is
provided to read in the status of the interrupt lines and of the
power supply outputs. Another 8-bit port is used to read the
interrupt status of modem transceivers 300.
DSL multiplexer 252 supports either (a) DC inputs (with internal
DC-DC converters), for the Telco environment or (b) AC inputs (with
internal SMPS) for corporate environments. In the Telco case, dual
redundant DC-DC converters and in the corporate case, dual
redundant SMPSs will be mounted inside the unit. Each of these will
provide 5V, 3.3V and +/-15V with sufficient current to drive the
electronics. The power supplies used will be having the protection
diodes and the corresponding outputs will be shorted together. A
faulty power supply can be without shutting down DSL multiplexer
252.
Since DSL multiplexer 252 is a store-and-forward device, data
forwarding module 510 receives data on the ADSL modem lines which
is multiplexed and sent over the 100 Mbps Ethernet port 302 (FIG.
3). The source MAC address of these packets are stored in an
address table that pairs subscriber line number with MAC addresses.
This address table will be needed when a frame is received over 100
Mbps Ethernet port 302 in order to perform data demultiplexing. The
destination MAC address in the frame is used to index the table and
identify the subscriber line to which the data has to be sent. The
software in DSL multiplexer 252 comprises two components: Boot code
and Runtime code. The Boot code resides in EPROM 316 and is invoked
at power-on. It initializes the processor and executes the power-on
diagnostics code. If fatal errors are seen, the boot code will
blink the health LED and display the error code on the DSL status
LEDs. and do nothing further. If the tests pass, and if Runtime
code is present in the flash EPROM 314, the boot code will then
decompress and move the runtime code from flash memory 314 to local
memory 306 and transfer control to the runtime code. If the runtime
code is not present in flash memory 314, the code is downloaded
from a TFTP server either through the serial link, the 10Base-T
link or through the 100Base-T link. The boot code also contains a
debugger, configuration utility and diagnostic utility over the
RS232 port.
The architecture of the runtime code is shown in FIG. 5. A
supervisory module 500 has an initialization module and a
scheduler. The initialization module does all the startup
initialization. The scheduler executes the different tasks defined
in the software in a round-robin fashion. The main functions of the
runtime code include: forwarding the data from the ADSL lines to
100Base-T port 302, demultiplexing and forwarding data from
100Base-T port 302 to the ADSL lines, controlling the operation of
the modem transceivers 300, and sharing the modem transceivers 300
among the 24 subscriber lines. The Runtime code also includes a
SNMPv2 based agent. The Boot code architecture is shown in FIG. 4.
A processor initialization module 400 initializes the serial port,
and the processor control structures on power-up/reset. Then, the
power-on diagnostics are run.
A power-on diagnostics module 402 performs tests on the various
hardware blocks. The result of the diagnostics is stored in NVSRAM
318. If the tests are passed, the green "Health" LED will blink at
a slow rate of 1 second on and 1 second off. A supervisory module
404 downloads the runtime code from flash memory 314 to local
memory 306 and executes it. If the runtime code is not present in
flash memory 314, the code is downloaded from the TFTP server.
supervisory module 404 is a simple control loop with tasks executed
in a round-robin fashion.
A TFTP module 406 is used for downloading the runtime code from a
TFTP server and uploading the code to a server if needed. A UDP/IP
stack 408 the protocol modules IP and UDP. A PPP module 410
implements the PPP protocol. A flash utilities 412 stores runtime
code in flash memory 314 in compressed form, and contains all the
functions related to flash memory 314 read/write routines and
compression-decompression algorithms. A 100Base-T driver 414 and a
10Base-T driver 416 are each used during execution of Boot code for
downloading the runtime file from the TFTP server, if required.
Driver 414 controls the operation of sending Ethernet packets,
receiving Ethernet packets and allocation and management of receive
and transmit queues. A serial driver 416 is used during execution
of Boot code for printing debug messages and also for downloading
the runtime code during testing. The serial driver controls the
operation of the serial interface chip. A debugger 418 comprises
typical debugger functionality, and also includes a menu driven
interface for local diagnostics. A configuration utility 420 allows
the user to configure the DSL multiplexer 252. The user can access
this utility through the serial port. System utilities 422 include
a timer and memory buffer functions.
Initially, when the runtime code is launched, a modem pool module
502 connects a CO modem to each of the subscriber lines in turn.
For each connection, the line parameters such as maximum upstream
and downstream speeds, receiver equalizer coefficients, etc are
retrieved from the modem and stored in a database in memory. This
database will be used later to "reestablish" a connection.
Modem-pool module 502 "scans" all unconnected lines, in rotation,
using free modems (if no free modem exists, it will not scan). If
more than one free modem are available, the scanning will be done
on many lines in parallel. After connecting the CO modem to a
particular line, the line parameters of that line will be stored to
the CO modem and a local warm startup command (ATT_LCL_WARM_REQ) is
given with a max time-out of 3 second. The CP modem 220 will detect
this command and will respond to the warm startup and both CO modem
and CP modem will come to the data mode. If the CP modem 220 has no
data to transfer it will issue a local standby command
(ATT_LCL_STBY_REQ) immediately. When the inactivity is detected by
CP modem 220 at the Ethernet port (no data for more than TBD
minutes, may be one minute) the CP modem 220 issues a local standby
command. The CO modem in the DSL multiplexer 252 will detect this
condition and will go to the standby mode and release the modem to
the free pool.
A RADSL transceiver driver 504 controls the operation of the ADSL
transceivers present on the card. RADSL transceiver driver 504
handles start-up of the CO modems, and setting up the parameters
and reading status of the CO modems. An ADSL driver 506 controls
the operation of RACs 308, 309 (GT-96010's) interfaced with
transceivers 300. ADSL driver 506 sends and receives packets over
the ADSL line using the HDLC-like framing mode. The parameters
downstream baud rate, constellation, noise margin, transmit power
level etc. are stored in the NVRAM 318.
100 Mbps Ethernet port driver 508 provides the up-link to the data
network. 100 Mbps Ethernet port driver 508 controls the operation
of sending Ethernet packets, receiving Ethernet packets and
allocation of receive and transmit queues. This also handles the
switching to the secondary link when the primary link fails.
A SNMP and MIBs module 512 implements the SNMPv2 protocol and thus
provides management and statistics collection through both in-band
and out-of-band SNMP links.
A UDP/IP stack are implemented in a UDP/IP module 516. Minimal
routing functions are implemented in the IP layer, to allow various
network management configurations. DSL multiplexer 252 will route
SNMP packets destined for other DSL multiplexers 252 as follows:
(a) packets received on the serial port will be sent either to the
10Base-T port or to the 100Base-T port depending on the routing
table, (b) packets received on the 10Base-T port will be sent on
the 100Base-T port. (response packets follow the reverse path.)
Routing tables will be manually entered by the operator via the
configuration utility; they will not be dynamically updated by the
IP module.
10Base-T driver 518 controls the operation of the 10Base-T Ethernet
interface. 10Base-T driver 518 performs the functions of: sending
Ethernet packets, receiving Ethernet packets, and allocation and
management of receive and transmit queues.
A PPP module 520 implements the point to point protocol (PPP) and
interacts with a serial driver 522 which controls the operation of
the serial interface chip
A proprietary protocol handler 524 is used for sending/receiving
proprietary protocol packets on the ADSL interface for managing CP
modem 220.
The following parameters have to be passed from DSL multiplexer 252
to multimedia switch 260: presence of DSL multiplexer 252 on a Fast
Ethernet port, current ADSL link speed on each one of the CP modems
220 connected to DSL multiplexer 252, MAC address of end station
210 connected to each CP modems 220.
DSL multiplexer 252 sends unsolicited Ethernet packets to
multimedia switch 260 at regular intervals. At present the time
interval between two successive packets is fixed, for example at
300 seconds. A MIB variable will be provided to configure this
parameter. The interval is kept large enough so as not to consume
any significant bandwidth on the 100Base-T link. Multimedia switch
260 can request DSL multiplexer 252 for any of the above parameters
at any time. On receiving such a request, DSL multiplexer 252
responds with a packet containing the value of the requested
parameter.
FIG. 6 is a graphical representation of a standard Ethernet type II
(DIX) packet format 600. A type field 602 in the Ethernet packet is
a value greater than or equal to 0800h. This gives the SAP number
of the protocol destined to receive this packet. Multimedia switch
260 and DSL multiplexer 252 use a proprietary type value of FFF0h
for sending their protocol packets.
A data field 700 of the protocol PDU is graphically represented in
FIG. 7. A command field (CM) 702 comprises one byte, a total length
(TL) field 704 comprise two bytes and includes the command field
702. A sequence number (SN) field 706 comprises one byte. A type
(T) field 708, a length (L) field 710 and a value (V) field 712 are
also provided.
The command field 702 can have the following values:
01h Request parameter (REQ) 02h Report Parameter (REP) 03h
Unsolicited parameter update (UPU) 04h Keep-alive (KA) 0ffh
Acknowledgement (ACK)
More enumerations will be added as and when necessary.
The values of command field 702 are used in a protocol administered
between DSL multiplexer 252 and multimedia switch 260. After start
up and initialization, DSL multiplexer 252 starts sending
keep-alive (KA) packets on its 100Base-T port 302 once in 5
minutes. This packet will have CM=4, LN=4 and no TLV fields 708,
710, 712. SN field 706 will start from 0 and gets incremented for
every subsequent packet. This field wraps around to 0 after ff.
If multimedia switch 260 receives this packet, it sends an
acknowledgement (ACK) packet to DSL multiplexer 252. This packet
will have CM=ff, LN=5, SN same as the value in the received KA
packet and no TLV fields. One byte, immediately after the SN field
706 contains the value of CM field 702 that was in the received KA
packet.
To start with, DSL multiplexer 252 initializes its 5800_discovered
flag to FALSE. When DSL multiplexer 252 gets an ACK for the
keep-alive packet, it sets 5800-discovered flag to TRUE. Further
on, if it does not get an ACK packet for 2 successive KA packets,
it resets 5800-discovered flag to FALSE. However, DSL multiplexer
252 will continue to send KA packets.
Multimedia switch 260 initializes its per-port 5300_discovered flag
to FALSE. If multimedia switch 260 receives a KA packet on a port,
the 5300_discovered flag for that port is set to TRUE. Further on,
if multimedia switch 260 does not receive a KA packet on a port for
2 minutes, the 5300_discovered flag for that port is set to
FALSE.
If the 5800_discovered flag is TRUE, DSL multiplexer 252 sends an
unsolicited parameter update (UPU) packet when it detects any
change in the exchanged configuration parameters. The UPU packet
will also be sent with all the parameters when the 5800_discovered
flag changes from FALSE to TRUE.
The UPU packet contains variable number of the following TLV
fields: (a) a MAC address having a type field of one byte, a length
field of eight bytes, a value field of six bytes of DSL multiplexer
MAC address; (b) link speed having a type field of two bytes, a
length field of five bytes, and a values field of 3 bytes--1 SL
number, 2 link speed upstream, 3 link speed downstream; and (c) a
port MAC address having a type field of three bytes, a length field
of nine bytes, and a value field of seven bytes. The seven bytes of
the value field correspond to SL number (1) and MAC address (2-7).
When multimedia switch 260 receives a UPU packet, it updates its
database with the information contained in the packet. Then it
sends an ACK packet for the UPU packet.
Multimedia switch 260 can any time send a Request Parameter (REQ)
packet to DSL multiplexer 252 on one of its ports. This packet will
have the following format:
CM 01h T Type of the requested parameter L 03h V SL number
DSL multiplexer 252 can request multiple parameters in a single
PDU.
When DSL multiplexer 252 gets a REQ packet from multimedia switch
260, it fills the values of all requested parameters in the REQ PDU
and sends a Report Parameter (REP) PDU to multimedia switch 260.
The REP PDU fields are given below:
CM 02h SN Same as in the REQ PDU T Type of the parameter L Length
of the TLV field V SL number and value.
FIG. 8 illustrates a generic PDU format 800 for exchanging
proprietary protocol between modem 220 and DSL multiplexer 252.
Generic PDU format 800 includes an Ethernet header 802, a DSL
multiplexer header 804, data field 806, and two bytes of check sum
808. An Ethernet header 802 comprises a source MAC which contains a
10BaseT MAC address of CP Modem 220 when a PDU is originating from
the modem 220. When the PDU originates from the CO DSL multiplexer
252, this field contains its 10BaseT/100BaseT Ethernet Port's MAC
address.
Ethernet header 802 also includes a destination MAC which contains
a broadcast MAC address irrespective of whether the packet is
originating from modem 220 or CO DSL multiplexer 252. Ethernet
header 802 has a type/length which should contain 0 to uniquely
differentiate between a Standard Ethernet packet and a DSL
multiplexer 252 packet on the ADSL link. Standard Ethernet Packets
will have a non-zero value for this field which signifies that the
packet format is either DIX or IEEE.
The DSL multiplexer 252 can be managed through the console port,
10Base-T port or 100Base-T port. The DSL multiplexer 252 will
provide SNMP proxy functionality for allowing management of the CP
modems connected to it. A proprietary protocol will be used between
the CP & DSL multiplexer 252 to transact management information
between them. This protocol will be transparent to the NMS. The DSL
multiplexer 252 maintains the latest management information from
all the CPs connected to it. This information will be obtained by
the DSL multiplexer 252 through periodic polling of the CP modems
220 which are currently on-line. The DSL multiplexer 252 routes the
management traffic among the following 3 ports: 10Base-T, 100Base-T
and Console Port. Hence, each of these ports has to be allocated an
IP address (belonging to different subnets). This will enable an
NMS present on any of these 3 subnets to manage other DSL
multiplexer 252s within the Telco. The DSL multiplexer 252 will use
statically configured routing table entries for routing.
The Ethernet switch 260 as detailed above works in conjunction with
the end-user-workstation's software to quickly deliver multimedia
information while ensuring an end-to-end negotiated quality of
service that is free from delay inducing congestion. The
end-station executes a shim software. The shim comprises a protocol
combination, or other suitable combination of protocols, to allow
the implementation of CIF technology to bring native ATM services
to desktops that are equipped with legacy Ethernet or Token Ring
NICs by encapsulating cells into frames. CIF can also be viewed as
the inverse of ATM LAN Emulation (LANE). LANE provides a way for
legacy LAN media access controller-layer protocols like Ethernet
and Token Ring, and all higher-layer protocols and applications, to
access work transparently across an ATM network. LANE retains all
Ethernet and Token Ring drivers and adapters; no modifications need
to be made to Ethernet or Token Ring end stations. In other words,
CIF emulates ATM services over frame-based LANs. CIF uses software
at the workstation without requiring the procurement of a new NIC
to support quality of service scheduling and ABRIER flow
control.
To achieve end-to-end quality of service, the shim resides as a
layer in end station to provide encapsulation of cells within
Ethernet frames in the desktop for transport to the data network.
Shim supports multiple queues, a scheduler (not shown), the ER flow
control, and header adjustment. Shim comprises an ATM Adaptation
Layer (AAL) which is the standards layer that allows multiple
applications to have data converted to and from the ATM cell. AAL
is protocol used that translates higher layer services into the
size and format of an ATM cell. The CIF shim layer also includes a
traffic management (TM) component that sets forth the congestion
control requirements. The TM component (not shown) can be
implemented as TM 4.0. The ATM Forum has developed a complete 4.0
protocol suite that includes UNI signaling 4.0 which allows
signaling of bandwidth and delay requirements for QoS; whereby, TM
4.0 which specifies explicit rate flow control and QoS
functions.
CIF shim layer also includes a frame segmentation and reassembly
(SAR) sublayer (not shown) which converts protocol data units
(PDUs) into appropriate lengths and formats them to fit the payload
of an ATM cell. At the destination end station, SAR extracts the
payloads for the cells and converts them back into PDUs which can
be used by applications higher up the protocol stack. The shim adds
the CIF header to packets before they are transmitted, and removes
the header when they are received. The shim manages the message
queues by queuing outgoing data into multiple queues for QoS
management. Shim also processes the RM cells for explicit rate flow
control using the ABR flow control and allows ATM signaling
software to run both native ATM application as well as standard IP
applications.
End station further comprises a device driver and a Network Device
Interface Specification (NDIS) layer 609 located above the CIF shim
layer 611. The end station 714 includes Internet Protocol (IP)
layer 607b which supports classical IP, LANE and MPOA for the
interworking of dissimilar computers across a network. IP layer
607b is a connectionless protocol that operates at the network
layer (layer 3) of the OSI model. Winsock 2.0 603 is the
application program interface (API) layer, which enables developers
to take advantage of ATM's QoS and traffic management features.
Application layer 601 can accommodate traditional as well as native
ATM applications. Native ATM applications can be readily created
with Winsock 2.0 API 603.
The shim arrangement guarantees that the services negotiated by the
native ATM applications for the VCs are not arbitrarily disrupted
by the traffic generated by the legacy applications. Forcing both
the ATM and the legacy protocol traffic to go through CIF shim
allows CIF shim to manage the transmission of all traffic according
to the QoS specified for each traffic stream. To support the
migration of legacy applications, the CIF AD forwards CIF traffic
from the conventional LAN onto the ATM infrastructure for delivery
to an ATM attached end station or to another CIF AD. The CIF ES is
also required to run LANE, MPOA (Multiprotocol Over ATM), or
Classical IP protocols. Network data from a legacy application is
first handled by the legacy protocols (e.g., TCP/IP), and then
turned into ATM traffic by LANE, MPOA, or Classical IP. The CIF ES
function encapsulates the individual cells into CIF frames before
data is finally transmitted on the wire to the CIF AD.
The enhancements in the network as discussed above can be
implemented if the end-user is shielded from any bottlenecks that
will negate such enhancements; the bottleneck typically exists at
the access link. Thus, the method of access needs to be made fast
and reliable.
While this invention has been described in connection with what is
presently considered to be the most practical and preferred
embodiments, it is to be understood that the invention is not
limited to the disclosed embodiments, but, on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims.
* * * * *